   ([out type] (writer out type {}))
   ([^OutputStream out type opts]
      (if (#{:json :json-verbose :msgpack} type)
-       (let [handlers (merge (default-write-handlers) (:handlers opts))]
+       (let [handlers (merge default-write-handlers (:handlers opts))]
          (Writer. (TransitFactory/writer (transit-format type) out handlers)))
        (throw (ex-info "Type must be :json, :json-verbose or :msgpack" {:type type})))))
 

(defn- transit-format
  "Converts a keyword to a TransitFactory$Format value."
  [kw]
  (TransitFactory$Format/valueOf 
   (str/join "_" (-> kw
                     name
                     str/upper-case

                   (aset next-key 0 marker)
                   (assoc! m k item)))))
           (complete [_ m] (persistent! m))))))
   })

(defn map-builder
  "Creates a MapBuilder that makes Clojure-
